Graffiti briefcase for stealth tagging

We’re floored by painter and engineer [Bob Partington’s] graffiti briefcase, which proves how well art and tech can complement one another. Fear not, Arduino haters, [Bob]’s case is an analog dream: no microcontrollers here.

The guts consist of 2 components: a linear drive system and a trigger assembly. The former takes advantage of a small RC motor with a chain drive which slides the can’s mounting unit along two stainless steel rods. The latter includes a custom wound solenoid plugged into a 24V cordless drill battery, which slams down 5 pounds of force onto the can’s nozzle to fire the paint.

This all fits into an otherwise inconspicuous looking briefcase to provide some urban camouflage. The final component is a stencil, which slides into a rectangular hole on the bottom of the case. The paint can sprays downward through the stencil and tags the ground at the touch of a brass button located near the handle.  [Bob] has plenty of other cool inventions you should check out that are less illegal. Or, stick it to the man by automating your tagging with Time Writer.

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[Update] Vladimir’s Robot Guitar


[Vladimir Demin] is somewhat of a legend for us; in his spare time he’s been mastering the automation of musical instruments. This time he’s back with upgrades to his build and four new videos. [Vladimir’s] top priority was to rework the strumming mechanism that earlier ran on solenoids. He’s improved the sound quality and reduced the clicks by swapped to stepper motors and overhauling the software.

Compared to his earlier setup, this one sounds more soulful and less automated, but [Vladimir] admits that it’s still not good enough and that he’s working on a new, brilliant implementation. Until then, take a few minutes and check out the rest of the videos below, then join us in scratching our heads in amazement: everything is built with simple hand tools.

[Vladimir] has come a long way, and it started with this Bayan (button accordion). Last year’s guitar build is also worth a look, as well as an in-depth interview.

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Keurig hack now automatically fills the water reservoir


This hack makes your Keurig experience fully automatic. For those that aren’t familiar with the hardware: this type of coffee maker includes a water reservoir. Coffee is brewed One cup at a time by drawing from that water, quickly heating it, then forcing it through disposable pods containing coffee grounds and a filter. This takes the user-friendly design one step further by automatically keeping the water full.

This goes beyond the last water reservoir hack we saw. That one routed a water line to the machine, but included a manually operated valve. [Eod_punk] added a solenoid valve and level sensor in this project. The level sensor is submerged in the tank and is monitored by a Basic Stamp microcontroller. When the level is low the BS1 drives the solenoid via a transistor, letting the water flow. This is all shown in the video below.

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Automatic tubular bells given a MIDI interface too


We’ve got to say it… these tubular bells sound awful! They don’t really have a tight pitch center so they sound really out of tune to us. But we think that’s the failing of the instrument itself and not the work which [Tolaemon] did to automate the instrument.

There are three main parts to his project. The first, which is shown above, adds a hammer for each bell. The hammers are hinged, with one side being pulled by a solenoid in order to strike the bell. The second part of the hack also uses solenoids, dampening the bell’s ability to ring by pressing a felt pad up against the bottom of the tube. The final portion of the project brings it all home by adding MIDI control to the hardware.

The clip after the break gives a good overview of the different features including some preprogrammed playback as well as direct control of the instrument using an electric keyboard. This reminds us of that scratch-built solenoid xylophone.

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Building a linear motor


We admit that this project doesn’t have very many details available, but it was just too neat for us to pass up. It’s a small linear motor which [ligonapProduktion] built after seeing a very brief description of a commercially available version.

The video after the break shows him testing the motor. In this screenshot he’s holding the center shaft while the coil assembly moves back and forth. But it works with a stationary coil moving the rod as well. The motor is basically a modified solenoid. There are sixteen neodymium magnets inside the shaft. The set of four coils is driven by an ATtiny44. Just like a stepper motor, energizing the coils in the correct order pushes against the rare earth magnets creating motion.

We’re not sure if he has any use in mind for this build. For us we just like to see the concept in practice (we feel the same way about a homopolar motor build).

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Wooden box repeats rhythm used when knocking on the lid


[Paul Mandel] just finished building this knock box project. It’s a familiar concept that uses a solenoid to tap on the side of the box. The Arduino driven setup monitors vibrations on the lid. When you knock on the box, it records the pattern and plays it back using the solenoid.

He was inspired by a knock-detecting door lock. Using that code as the starting point he implemented a system that takes input from a simple push button and echos back the rhythm using the Pin 13 LED on the Arduino board. This is a great way to start as it removes the complexity of driving a solenoid and monitoring a piezo element. After a bit of success he implemented each of those hardware modules one at a time. You can get a look at the final product in the clip after the break.

One of our favorite version of this project is still the knock block from several years back.

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A harpsichord that plays itself

[Malcolm Messiter] is an Oboe player who loves to play pieces from the Baroque era. This often means playing with a Harpsichord and he managed to acquire one to call his very own. Unfortunately you can’t play both instruments at once so he set out to automate the keyboard. What you see here is a fully working version, but he soon went on to add solenoids to the upper rank as well. His story starts on page 27 of this newsletter (PDF).

He really went out of his way to make sure the instrument was not mistreated. A cabinet-maker built some brackets to mount the system above the keys. A friend drilled and tapped a sheet of acrylic to which each solenoid was mounted. The solenoid shafts have each been padded with felt to cushion the blow on the keys. We’ve embedded two demo video after the break that show off the first and second versions of the builds.

Harpsichords pluck the strings instead of hitting them with a hammer as the piano does. The mechanism that does the plucking had worn out on many of the keys so [Malcolm] used a 3D printer to help replace them.

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